Heat
Chapter 5: Heat
- 4.A calorimeter has mass 100 g and specific heat 0.1 kcal/ kg °C. It contains 250 gm of liquid at 30°C having specific heat of 0.4 kcal/kg °C. Answer: about 20.8 °C Convert specific heats: 0.1 kcal/kg °C = 0.1 cal/g °C and 0.4 kcal/kg °C = 0.4 cal/g °C. Take the latent heat of melti... 1
- A thermally insulated pot has 150 g ice at temperature 0°C. How much steam of 100°C has to be mixed to it, so that water of temperature 50°C will be obtained? Answer: about 33 g of steam Let the mass of steam be m g. Heat gained by ice (melts at 0 °C, then warms to 50 °C): 150×80 + 150×1×50 = 12000... 1
- Liquid ammonia is used in ice factory for making ice from water. If water at 20°C is to be converted into 2 kg ice at 0°C, Answer: about 586.5 g of ammonia Heat to be removed from the water (mass 2 kg = 2000 g, specific heat 1 cal/g °C, latent heat of fusion of i... 1
- Equal heat is given to two objects A and B of mass 1 g. Temperature of A increases by 3°C and B by 5°C. Which object has more specific heat? And by what factor? Correct answer is 5/3 https://youtu.be/vENdt48i2W4 2
- 8. Read the following paragraph and answer the questions. i. Heat is transferred from where to where? Ans: Heat is transferred from the object at higher temperature to the object at lower temperatur... 1
- d. On what basis and how will you determine whether air is saturated with vapour or not? On the basis of amount of water vapours present in the air, it can be either saturated or unsaturated. If the amount of water vapours exceed... 1
- c. Explain the role of latent heat in the change of state of a substances? According to the kinetic model, the total energy of a molecule is the sum of kinetic energy due to its motion (which depends on temperature)... 1
- b Which principle is used to measure the specific heat capacity of a substance? If a system of two objects is isolated from the environment by keeping it inside a heat resistant box, then no energy can leave the box or e... 1
- a. What is meant by latent heat? How will the state of matter transform if latent heat is given off? The amount of heat needed to change the state of unit mass of the body from solid to liquid or from liquid to gas without any change in temp... 1
- c. In cold regions in winter, the rocks crack due to anomalous expansion of water. Water has the property of expanding below 4^oC, is called the anomalous behaviour of water. Thus, in cold regions when the temperature falls... 1
- b. How can you relate the formation of water droplets on the outer surface of a bottle taken out of refrigerator with formation of dew? If the temperature of unsaturated air is decreased, a temperature is reached at which the air becomes saturated with water vapour. In both t... 1
- a. What is the role of anomalous behaviour of water in preserving aquatic life in regions of cold climate? The anomalous behaviour of water is that it contracts from 0^oC to 4^oC and beyond 4^oC it expands. Thus, the density of water is maximum at... 1
- Explain the following temperature versus time graph. In the given graph, line AB represents conversion of ice into water at constant temperature. When ice is heated, it melts at 0^oC and conver... 1
- While deciding the unit for heat, which temperatures interval is chosen? Why? While deciding the unit for heat (which is calorie), the temperature interval chosen is 14.5^oC-15.5^oC. We know that the amount of heat rel... 1
- What is meant by specific heat capacity? How will you prove experimentally that different substances have different specific heat capacities? The amount of heat energy required to raise the temperature of a unit mass of an object by 1 °C is called the specific heat capacity of that... 1
- 2. Observe the following graph. Considering the change in volume of water as its temperature is raised from 0 o C, If the temperature of water is raised from 0 °C to 10 °C, its volume goes on decreasing in the range 0 °C to 4 °C. It is minimum at 4 °C. Th... 1
- 1. Fill in the blanks and rewrite the sentence. a. The amount of water vapour in air is determined in terms of its--------- Answer: The amount of water vapour in air is determined in terms... 1